The present invention relates to a method for manufacturing a stator core and a rotor core of an electrical rotating machine such as a motor.
For example, Japanese Laid-Open Patent Publication No. 2006-223022 discloses a method for manufacturing such an electrical rotating machine. According to the method disclosed in the document, a workpiece, which is a belt-like steel plate, is conveyed intermittently in its longitudinal direction. While the workpiece is in the stopped state, core pieces are punched out of the workpiece. Next, a push-back operation is performed in which the punched out core pieces are pushed back into the punching hole. When the workpiece is conveyed to the next processing step, the core pieces are pushed out of the workpiece, and lined up on a table. Core plates are thus formed and laminated to form a core.
In the above described manufacturing method, core pieces are pushed back into the punching holes. This is likely to form deficiencies such as burrs at the outer periphery of the core pieces. Accordingly, a polishing process needs to be performed to remove burrs. If burrs or scratches are left unattended, the magnetic property will deteriorate, which can lower the performance of the core. To deal with such problems, a core plate may be formed at a position where core pieces are punched out, without performing the push-back operation after core pieces are punched out. However, to punch core pieces at a position where a core plate is formed, an annular die that has a shape corresponding to the entirety of the core pieces is required. When an annular die is employed, a space having a dimension corresponding to the thickness of the die is needed on either side of a punched out core piece. It is therefore impossible to line up core pieces without spaces in between, and core plates cannot be produced.